Replacing the Firewall Grommet for the Main Wiring Harness

[doitwright]

The one thing I was most concerned about when disassembling my SL was how would I get those wires back through the firewall and replace the totally worn firewall grommet. It is amazing what one thinks about at night when lying awake in bed. So here it is. My solution for fitting a square peg through a round hole.

Keep in mind I did this with the wiring harness removed from the car.

Go to Plumbing Section at your Home Depot or local hardware store and pick up one each a plastic 1-1/4" and 1-1/2" sink tail piece. Do not try this with regular PVC DWV pipe. The wall is too thick. Some petroleum jelly might aid in getting the grommet to slip onto the tail piece.

Make 4 cuts at the end of each tail piece (without the flange) at least 4" long and 90 degrees to each other. That should leave you with 4 cuts.

Start with the 1-1/4" piece and squeeze the cut end so the 4 sections of the pipe start to overlap each other.

While holding the overlapping sections tightly together, insert the cut end into the new grommet.

Once you have the tail piece through the grommet hole, push the pipe through until you get past the cut section and on to the uncut section of your tail piece. The rubber will expand to the larger opening.

I found that 1-1/4" was not large enough to get some of the larger connectors on the wire harness through the grommet so going to the next size tail piece (1-1/2") was just large enough.

The next step is to transfer the grommet from the 1-1/4" to 1-1/2" tail piece.

It was also easier to transfer from the 1-1/4" to 1-1/2" than trying to start with the 1-1/2".

Once you have your grommet fit to the 1-1/2" tail piece, trim the pipe to slightly more than the length of the grommet.

Now you are ready to pass your wires through the grommet.

Once you get the grommet to the same location where your old grommet was located, slide the pipe out of the grommet and cut the plastic pipe to remove it.

There you go.

Here is the link to my google album if you want to see the photos when I did this.

https://photos.app.goo.gl/NJg6gmEt5q6uL6M38

[dirkbalter]

Appreciated,
thank you.

[ja17]

Normally done with all the connectors removed. Lots of work. Hope your new method works.

[doitwright]

The method works. Photos show the process and results.

[johnk]

Thanks Frank! This is my next step to complete.

John

[450sl]

I have these pliers , would gladly donate to forum.

[mBdrvr]

The guy before me didn't bother with the grommet. Any suggestions on what to use with the wire loom already installed??

[Dave H]

Cut through one side with a craft knife, fit it over and glue with tyre adhesive, possibly use a couple of cable ties to hold it together while the glue goes off, you won’t be able to tell it was ever cut if you do a neat job.

Its a similar job to replacing a CV boot only easier .

[johnk]

I used Frank's method last night. Saved me a lot of time. Took about an hour to hour and a half slide the grommet onto the 1 1/2 inch pipe and then slide into place on the wiring harness. I only had to take a part a couple of the connectors at the end when I had too much wire already in the tube to also slide a connector through.

[mBdrvr]

Thanks Dave. I'll give that a try.

Paul